Difference between revisions of "1999 IMO Problems/Problem 1"

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Upon reading this problem and drawing some points, one quickly realizes that the set
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Revision as of 19:27, 12 November 2023

Problem

Determine all finite sets $S$ of at least three points in the plane which satisfy the following condition:

For any two distinct points $A$ and $B$ in $S$, the perpendicular bisector of the line segment $AB$ is an axis of symmetry of $S$.

Solution

Upon reading this problem and drawing some points, one quickly realizes that the set

Alternate solutions are always welcome. If you have a different, elegant solution to this problem, please add it to this page.